Thermal fluctuations and anomalous elasticity of homogeneous nematic elastomers

We present a unified formulation of a rotationally invariant nonlinear elasticity for a variety of spontaneously anisotropic phases, and use it to study thermal fluctuations in nematic elastomers and spontaneously anisotropic gels. We find that in a thermodynamic limit homogeneous nematic elastomers are universally incompressible, are characterized by a universal ratio of shear moduli, and exhibit an anomalous elasticity controlled by a nontrivial low temperature fixed point perturbative in D=3-epsilon dimensions. In three dimensions, we make predictions that are asymptotically exact.Comment: 4 RevTeX pgs,,submitted to Europhysics Letter

Anomalous elasticity of nematic elastomers

We study the anomalous elasticity of nematic elastomers by employing the powers of renormalized field theory. Using general arguments of symmetry and relevance, we introduce a minimal Landau-Ginzburg-Wilson elastic energy for nematic elastomers. Performing a diagrammatic low temperature expansion, we analyze the fluctuations of the displacement fields at and below the upper critical dimension 3. Our analysis reveals an anomaly of certain elastic moduli in the sense that they depend on the length scale. In $d = 3$ this dependence is logarithmic and below $d=3$ it is of power law type with anomalous scaling exponents. One of the 4 relevant shear moduli vanishes at long length scales whereas the only relevant bending modulus diverges.Comment: 4 page

Investigation of microstructural damage to eutectic carbides from scratch tests of a heat-treated Fe–Cr–W–Mo–V–C alloy

The characteristics of abrasive wear damage to the carbides and eutectic phases in a Fe–Cr–W–Mo–V–C alloy were systematically investigated using point scratch testing on heat-treated specimens with preserved eutectic structures from a characteristic eutectic carbide formation temperature of 1240 °C. A deep-etching method is applied to study the detailed morphologies of the eutectic carbides by optical microscopy (OM) and field emission scanning electron microscopy (FESEM). The types of the eutectic carbides were identified by X-ray diffraction (XRD) as V-rich eutectic MC and Mo-rich eutectic M2C. Single-pass scratch tests were carried out on polished and deep-etched surfaces of the specimens to investigate the micro-scale wear behavior of the eutectic carbides with and without protection by the matrix phase. It was found that, when a surrounding matrix is present, the micro-cracks initiate from the eutectic region during the scratch tests and slip-lines appear in scratched edges of the matrix phase. Without matrix protection as revealed in the deep-etched specimens, the main failure form is carbide dendrites break-off forming wear debris. The detailed differences in response and deformation mode of carbide microstructures with/without matrix support to single-point abrasion behavior are schematically depicted for main eutectic MC and M2C carbides under different loading conditions. Potential improvement on wear performance through the composition design is also discussed based on the different fracture and wear behavior of V-rich eutectic MC and Mo-rich eutectic M2C identified

An improvement of isochronous mass spectrometry: Velocity measurements using two time-of-flight detectors

Isochronous mass spectrometry (IMS) in storage rings is a powerful tool for mass measurements of exotic nuclei with very short half-lives down to several tens of microseconds, using a multicomponent secondary beam separated in-flight without cooling. However, the inevitable momentum spread of secondary ions limits the precision of nuclear masses determined by using IMS. Therefore, the momentum measurement in addition to the revolution period of stored ions is crucial to reduce the influence of the momentum spread on the standard deviation of the revolution period, which would lead to a much improved mass resolving power of IMS. One of the proposals to upgrade IMS is that the velocity of secondary ions could be directly measured by using two time-of-flight (double TOF) detectors installed in a straight section of a storage ring. In this paper, we outline the principle of IMS with double TOF detectors and the method to correct the momentum spread of stored ions.Comment: Accepted by Nuclear Inst. and Methods in Physics Research,

Coupled node similarity learning for community detection in attributed networks

© 2018 by the authors. Attributed networks consist of not only a network structure but also node attributes. Most existing community detection algorithms only focus on network structures and ignore node attributes, which are also important. Although some algorithms using both node attributes and network structure information have been proposed in recent years, the complex hierarchical coupling relationships within and between attributes, nodes and network structure have not been considered. Such hierarchical couplings are driving factors in community formation. This paper introduces a novel coupled node similarity (CNS) to involve and learn attribute and structure couplings and compute the similarity within and between nodes with categorical attributes in a network. CNS learns and integrates the frequency-based intra-attribute coupled similarity within an attribute, the co-occurrence-based inter-attribute coupled similarity between attributes, and coupled attribute-to-structure similarity based on the homophily property. CNS is then used to generate the weights of edges and transfer a plain graph to a weighted graph. Clustering algorithms detect community structures that are topologically well-connected and semantically coherent on the weighted graphs. Extensive experiments verify the effectiveness of CNS-based community detection algorithms on several data sets by comparing with the state-of-the-art node similarity measures, whether they involve node attribute information and hierarchical interactions, and on various levels of network structure complexity